In general, in ischemic heart diseases, a blood flow to the cardiac muscle is hindered due to occlusion, stenosis, etc. of a coronary artery, and the supply of blood becomes deficient or stops, leading to a failure of the heart. A symptom is a sensation of pain or compression mainly in the precordia or, in some cases, in the left arm or in the back. Therapeutic methods for patients with ischemic heart diseases are generally classified into bypass surgery, PCI (catheter surgery), and pharmacotherapy.
The bypass surgery is a therapeutic method in which, as illustrated in FIG. 20, some other blood vessel is connected to a blood vessel which is stenosed or occluded, thereby causing more blood to flow through this connected blood vessel to a region in which ischemia occurs.
PCI is a therapeutic method in which, as illustrated in FIG. 21 and FIG. 22, a therapeutic instrument with a thin tubular structure is directly inserted in a blood vessel in which occlusion or stenosis occurs, thereby forcibly expanding the blood vessel.
The pharmacotherapy is a therapeutic method for improving ischemia of the heart, or preventing formation of a thrombus.
There is known FFR (Fractional Flow Reserve) as an index which a doctor refers to when selecting any one of these three therapeutic methods.
In general, assessment of the degree of progress of stenosis is carried out by directly inserting a pressure wire into a blood vessel. The pressure wire is inserted, as illustrated in FIG. 23, and pressures Pin and Pout at regions in front of and behind a stenosed part are measured.
Here, the FFR is defined by Pout/Pin. If this value is lower than 0.8, the doctor selects the PCI as the therapeutic method. If this value is higher than 0.8, the doctor selects pharmacotherapy as the therapeutic method. However, since the measurement of the pressures Pin and Pout with use of the pressure wire is invasive, there is a demand for a non-invasive measuring method and FFR estimation method.
This being the case, in recent years, a simulation-based FFR estimation method using fluid analysis has been devised. An existing simulation is a simulation using 3D images. In the basic concept of such a simulation-based FFR estimation method, the shape of a blood vessel, which is obtained from modality, and physical parameters, such as a viscosity value, etc. of blood, etc., are used as inputs, and FFR is estimated (calculated) by using a Navier-Stokes equation which is used in, e.g. CFD (Computational Fluid Dynamics).
A problem with such 3D simulation is that a great deal of calculation time is required. Thus, such a problem arises that time is also needed until selecting a therapeutical method by using the FFR, and the 3D simulation is not suitable when there is no time to lose. As a measure for an improvement, there is a method in which the time needed for simulation is greatly reduced by executing 2D approximation of the simulation that uses 3D images.
Thereby, it becomes possible to quickly calculate FFR on the basis of simulation, and the doctor can use FFR as an effective index.
At present, however, it is not possible to assess the causal relationship between an ischemic cardiac muscle and a stenosed part to be treated, or to make risk assessment. Specifically, the FFR fails to be properly reflected on the assessment of the causal relationship between an ischemic cardiac muscle and a stenosed part to be treated, and on the risk assessment. Judgment as to, for example, which stenosed part is to be treated with top priority depends greatly on the empirical rule of doctors. Thus, such a problem arises that there is a concern of occurrence of a human error, such as unnecessary treatment or an oversight.
In addition, for example, in a coronary artery which contributes to myocardial infarction, since the blood flow volume and pressure decrease, the FFR apparently increases. Thus, despite such a serious symptom as myocardial infarction having been caused, the FFR is apparently high. In this case, too, such a problem arises that there is a concern of occurrence of a human error, such as an oversight of a symptom, or erroneous selection of a therapeutic method.
The object is to provide a medical image processing apparatus which can reduce the possibility of a human error.